Shrinkage and kinetic models for color changes of pretreated mushrooms with gamma irradiation during thin layer drying
Non-thermal processes such as irradiation are desierable methods to be used in combination with thermal ones in order to improve the quality of agricultural products. In this study, mushroom slices were initially irradiated under various doses (0 as control, 1.2, 2.4 and 3.6 kGy) and then dried at different temperatures (50, 60, 70 ºC). Then, the machine vision and image processing techniques were used to investigate any color changes and area shrinkage of dried mushroom slices. By increasing the irradiation dose, the change of the color indices (L* and b*), total color difference (ΔE), browning index and chroma decreased. While high temperatures had negative effect on these parameters except chroma. Moreover, the variation range of a* was insignificant during drying and the hue angle was between 70° to 78°. The zero and first order models for L*, b* and ΔE, as a function of drying time, showed high correlation coefficient for all treatments (0.91-0.99). Regarding shrinkage, by increasing irradiation dose and drying temperature, the area shrinkage slightly increased, where the temperature was more effective than irradiation dose.